Make CI and Docker builds survive an unreachable npm registry

The Gitea runner hung for over 30 minutes on `npm ci` because it cannot
reach registry.npmjs.org. The registry is now configurable through the
NPM_REGISTRY repository variable, passed on to the server's Docker
build, and npm gives up after bounded retries. Jobs also have time
limits (test 15 min, deploy 30 min) so the runner is never held forever.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Dockerfile

@@ -1,8 +1,10 @@
 # Stage 1: run the tests and build the static game with Vite.
 FROM node:22-alpine AS build
 WORKDIR /app
+# Override with a reachable mirror where registry.npmjs.org is blocked (docker compose passes NPM_REGISTRY).
+ARG NPM_REGISTRY=https://registry.npmjs.org/
 COPY package.json package-lock.json ./
-RUN npm ci --no-audit --no-fund
+RUN npm ci --no-audit --no-fund --registry="$NPM_REGISTRY" --fetch-retries=3 --fetch-timeout=60000
 COPY . .
 RUN node --test tests/*.test.js && npm run build